The present invention relates to catalytic structures formed of catalyst-carrying loosely packed fibers or filaments into and through which air-butane or other combustible gas mixtures may be flowed to generate flameless catalytic combustion, upon ignition, for such purposes as curling irons and other similar apparatus.
In earlier U.S. Pat. No. 4,399,185 of common assignee with the present invention, a satisfactory structure of this nature is disclosed in which the loosely packed fibers remain in matte form and are catalyzed in a manner that retains the required porosity and pressure drop characteristics, while remaining flexible enough to be formed into cylindrical or other desired geometrical shapes through which combustible gas-air mixtures may be flowed, for the above and other purposes. Such an approach, however, requires both a supporting hollow, gas-permeable or perforated internal mandril, dowel or form upon which the matte may be supported throughout its cylindrical form, and an external permeable cylindrical containing element, such as a helical spring or coil. In operation, the air-gas mixture is introduced along the interior of the internal mandril, escapes through the perforations or holes therein into the surrounding catalyzed matte fibers and through the interstices of the spring or coil or other external container, generating flameless combustion within and along the matte, upon ignition. WHile this structure has proven to be admirably successful for hair curling-iron applications, there are certain disadvantages thereto due to the inherent mechanical weakness and lack of uniformity of the matte. Specifically, it is necessary to hold the matte in cylindrical form by wrapping it around an internal supporting structure. This operation is not only costly in itself, but this disadvantage is seriously aggravated by holes often unavoidably produced in the mattes while routinely and rapidly wrapping them around an internal mandril or dowel. A significant rejection rate of, for example, hair curlers results from such defects because such holes cause waste of fuel and non-uniform excessive aging of the catalyst at "hot spots" generated at perforations of the mandril or dowel in the vicinity of such holes.